System and method for processing liquefied gas

ABSTRACT

The present invention relate to liquefied gas treatment system and method. A liquefied gas treatment system includes: a liquefied gas supply line connected from a liquefied gas storing tank to a source of demand, a heat exchanger provided on the liquefied gas supply line between the source of demand and the liquefied gas storing tank and configured to exchange heat between the liquefied gas supplied from the liquefied gas storing tank and heat transfer media, a media heater configured to heat the heat transfer media, a media circulation line connected from the media heater to the heat exchanger, a liquefied gas temperature sensor provided on the liquefied gas supply line, and configured to measure a temperature of the liquefied gas, and a controller configured to make the measured temperature of the liquefied gas be equal to or higher than a demanded temperature of the source of demand in such a manner that the controller decreases a flow rate of the heat transfer media flowing into the media heater. The liquefied gas treatment system and method of the present invention may decrease a circulation rate of the heat transfer media in such a manner that a difference between temperatures of the heat transfer media at front and rear ends of the heat exchanger is sufficiently maintained, thereby improving efficiency of circulation of the heat transfer media, and heating liquefied gas at an appropriate temperature to supply the heated liquefied gas to a source of demand.

TECHNICAL FIELD

The present invention relates to a liquefied gas treatment system andmethod.

BACKGROUND ART

Recently, with the development of technologies, liquefied gas, such asliquefied natural gas and liquefied petroleum gas, has been widely used,instead of gasoline or diesel.

Liquefied natural gas is gas obtained by cooling and liquefying methaneobtained by refining natural gas collected from a gas field, and iscolorless and transparent liquid, and produces few pollutants and has ahigh calorific value, so that the liquefied natural gas is a veryexcellent fuel. On the other hand, the liquefied petroleum gas is a fuelobtained by compressing and liquefying gas, of which main components arepropane (C₃H₈) and butane (C₄H₁₀), collected from an oilfield, togetherwith petroleum at room temperature. The liquefied petroleum gas iscolorless and odorless, similar to liquefied natural gas, and has beenwidely used as fuel for home, a business, an industry, and a vehicle.

The liquefied gas is stored in a liquefied gas storing tank installed ona ground, or a liquefied gas storing tank included in a vessel, which isa transportation means sailing the ocean, and a volume of the liquefiednatural gas is decreased by 1/600 by liquefaction, and a volume ofpropane is decreased by 1/260 and a volume of butane is decreased by1/230 by liquefaction in liquefied petroleum gas, so that storageefficiency is high.

The liquefied gas is supplied to and used in various sources of demand,and an LNG fuel supply method of driving an engine by using LNG as fuelin an LNG carrying vessel carrying liquefied natural gas has beenrecently developed, and the method of using LNG as the fuel of theengine has been applied to other vessels, in addition to the LNGcarrying carrier.

However, a temperature, a pressure, and the like of liquefied gasdemanded by a source of demand, such as an engine, may be different froma state of liquefied gas stored in a liquefied storing tank.Accordingly, in recent days, technology of supplying LNG to a source ofdemand by controlling a temperature, a pressure, and the like of theliquefied gas stored in a liquid state has been continuously researchedand developed.

DISCLOSURE Technical Problem

The present invention is conceived to solve the aforementioned problems,and an object of the present invention is to provide a liquefied gastreatment system and method which calculates a target temperature ofheat transfer media, which are heat exchanged with liquefied gas,through a measured temperature of the liquefied gas transmitted to thesource of demand and controls a flow rate of the heat transfer mediaflowing into a media heater or the amount of heat sources supplied tothe heat transfer media from the media heater based on the targettemperature of the heat transfer media, thereby efficiently controllinga temperature of the liquefied gas supplied to the source of demand.

Another object of the present invention is to provide a liquefied gastreatment system and method, which enables liquefied gas to be suppliedin a state appropriate to a demanded temperature of the source of demandthrough cascade control of calculating a target temperature of the heattransfer media based on a measured temperature of the liquefied gas andappropriately heating the heat transfer media at the target temperatureof the heat transfer media.

Another object of the present invention is to provide a liquefied gastreatment system and method, which enables at least some of heattransfer media to bypass the media heater according to a targettemperature of the heat transfer media, changes the amount of heattransfer media flowing into the media heater by driving a media pumpsupplying the heat transfer media to a media heater, or controls theamount of heat sources supplied to the media heater by the media heater,thereby easily controlling calories transmitted to the liquefied gas bythe heat transfer media.

Another object of the present invention is to provide a liquefied gastreatment system and method, which detects a temperature of the heattransfer media at a downstream of the heat exchanger and controls a flowof the heat transfer media so as to prevent a temperature of the heattransfer media from being decreased to a predetermined temperature orlower in order to prevent water included in the heat transfer media andthe like from being iced (icing phenomenon) due to supercooling of theheat transfer media due to the liquefied gas in the heat exchanger,thereby stably implementing the system.

Another object of the present invention is to provide a liquefied gastreatment system and method, which discharges heat transfer mediaflowing into the heat exchanger to the outside through a media dischargeline as necessary in order to prevent generation of a problem in drivingthe system due to the icing phenomenon by cooling of the heat transfermedia remaining in the heat exchanger by liquefied gas, therebyprotecting the heat exchanger and the system.

Another object of the present invention is to provide a liquefied gastreatment system and method, which adjusts the amount of heat transfermedia flowing into the media heater or the amount of heat sourcessupplied to the media heater in order to prevent water included in theheat transfer media and the like from being evaporated (crackingphenomenon) according to overheating of the heat transfer media in themedia heater, thereby efficiently using the heat transfer media.

Another object of the present invention is to provide a liquefied gastreatment system and method, which maintains a sufficiently largedifference between temperatures of the heat transfer media at the frontand rear ends of the heat exchanger so that liquefied gas is heated to ademanded temperature of the liquefied gas of the source of demand, anddecreases a circulation rate of the heat transfer media, therebymaximizing efficiency of the media pump.

Technical Solution

In accordance with an aspect of the present invention, there is provideda liquefied gas treatment system, including: a liquefied gas supply lineconnected from a liquefied gas storing tank to a source of demand; aheat exchanger provided on the liquefied gas supply line between thesource of demand and the liquefied gas storing tank, and configured toexchange heat between the liquefied gas supplied from the liquefied gasstoring tank and heat transfer media; a media heater configured to heatthe heat transfer media; a media circulation line connected from themedia heater to the heat exchanger; a liquefied gas temperature sensorprovided on the liquefied gas supply line, and configured to measure atemperature of the liquefied gas, and a controller configured to causethe measured temperature of the liquefied gas to be equal to or higherthan a demanded temperature of the source of demand in such a mannerthat the controller decreases a flow rate of the heat transfer mediaflowing into the media heater.

Particularly, the liquefied gas treatment system may further include: amedia tank configured to store the heat transfer media; and a media pumpconfigured to supply the heat transfer media stored in the media tank tothe media heater, in which the controller controls the flow rate of theheat transfer media supplied to the media heater from the media pump bycontrolling driving of the media pump.

Particularly, the controller may control the flow rate of the heattransfer media by adjusting RPM of the media pump.

Particularly, the liquefied gas treatment system may further include: aflow rate adjusting valve provided on the media circulation line, andconfigured to adjust the flow rate of the heat transfer media flowinginto the media heater, in which the controller may control the flow rateof the heat transfer media by adjusting a degree of opening of the flowrate adjusting valve.

Particularly, the liquefied gas treatment system may further include: amedia flow rate sensor provided on the media circulation line andconfigured to measure the flow rate of the media transfer media flowinginto the media heater.

Particularly, the liquefied gas temperature sensor may be providedbetween the heat exchanger and the source of demand on the liquefied gassupply line.

Particularly, the liquefied gas treatment system may further include: amedia state detecting sensor provided on the media circulation line, andconfigured to measure a state of the heat transfer media.

Particularly, the media state detecting sensor may detect a differencebetween temperatures of the heat transfer media at front and rear endsof the heat exchanger, and the controller may cause the differencebetween the temperatures of the heat transfer media to be equal to orgreater than a predetermined value in such a manner that the controllerdecreases the flow rate of the heat transfer media flowing into themedia heater.

Particularly, the media state detecting sensor may include: a firstmedia state detecting sensor configured to detect a temperature of theheat transfer media at a downstream of the media heater; and a secondmedia state detecting sensor configured to detect a temperature of theheat transfer media downstream of or in the heat exchanger, and thecontroller causes a difference between a measured temperature by thefirst media state detecting sensor and a measured temperature by thesecond media state detecting sensor to be equal to or greater than apredetermined value in such a manner that the controller decreases theflow rate of the heat transfer media flowing into the media heater.

Particularly, the liquefied gas treatment system may further include: apump provided on the liquefied gas supply line and configured topressurize the liquefied gas discharged from the liquefied gas storingtank, in which the heat exchanger exchanges heat between the liquefiedgas supplied from the pump and the heat transfer media.

Particularly, the heat transfer media may be glycol water.

In accordance with an aspect of the present invention, there is provideda method of driving a liquefied gas treatment system which heatsliquefied gas with heat transfer media in a heat exchanger, in such amanner that a media heater heats and supplies the heat transfer media tothe heat exchanger, the liquefied gas treatment method including:measuring a temperature of the liquefied gas supplied to the source ofdemand; and causing the measured temperature of the liquefied gas to beequal to or higher than a demanded temperature of the source of demandin such a manner that a flow rate of the heat transfer media flowinginto the media heater is decreased.

Particularly, the measuring of the temperature of the liquefied gas mayinclude measuring the temperature of the liquefied gas between the heatexchanger and the source of demand.

Particularly, the liquefied gas treatment method may further includedetecting a state of the heat transfer media.

Particularly, the detecting of the state of the heat transfer media mayinclude detecting a difference between temperatures of the heat transfermedia at front and rear ends of the heat exchanger, and the decreasingof the flow rate of the heat transfer media or calories supplied to theheat transfer media includes causing the difference between thetemperatures of the heat transfer media at the front and rear ends ofthe heat exchanger to be equal to or greater than a predetermined valuein such a manner that the flow rate of the heat transfer media flowinginto the media heater is decreased.

Particularly, the decreasing of the flow rate of the heat transfer mediamay include controlling driving of the media pump supplying the heattransfer media to the media heater.

Particularly, the controlling of the driving of the media pump mayinclude adjusting RPM of the media pump.

Particularly, the decreasing of the flow rate of the heat transfer mediamay include controlling a degree of opening of a flow rate adjustingvalve provided upstream of the media heater.

Advantageous Effects

According to the liquefied gas treatment system and method of thepresent invention, it is possible to induce a target temperature of heattransfer media through a measured temperature of liquefied gas at a rearend of the heat exchanger, adjust the amount of heat transfer mediaflowing into the media heater, and easily heat the heat transfer mediaat the target temperature, thereby enabling the liquefied gas to besupplied to a source of demand in a state appropriate to a demandedtemperature of the source of demand.

Further, according to the liquefied gas treatment system and method ofthe present invention, it is possible to enable at least some of heattransfer media to bypass the media heater, change the amount of heattransfer media flowing into the media heater according to driving of themedia pump, or control the amount of heat sources supplied to the mediaheater, thereby effectively controlling the temperature of the heattransfer media.

Further, according to the liquefied gas treatment system and method ofthe present invention, it is possible to control a degree of heating theheat transfer media based on a temperature of the heat transfer mediadetected in or downstream of the heat exchanger or at the downstream ofthe media heater in order to prevent water included in the heat transfermedia from being frozen or evaporated, thereby implementing smoothcirculation of the heat transfer media.

Further, according to the liquefied gas treatment system and method ofthe present invention, it is possible to enable the heat transfer mediato be discharged from the heat exchanger along the media discharge linewhen the heat transfer media flowing into the heat exchanger are cooledmore than needed by the liquefied gas, thereby preventing failure of theheat exchanger and shutdown of the system.

Further, according to the liquefied gas treatment system and method ofthe present invention, it is possible to decrease a circulation rate ofthe heat transfer media, sufficiently maintain a difference betweentemperatures of the heat transfer media at the front and rear ends ofthe heat exchanger, improve efficiency of circulation of the heattransfer media, and heat the liquefied gas at an appropriate temperatureand supply the heated liquefied gas to the source of demand.

DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram of a liquefied gas treatment system inthe related art.

FIG. 2 is a conceptual diagram of a liquefied gas treatment systemaccording to first to fourth embodiments of the present invention.

FIG. 3 is a flowchart of a liquefied gas treatment method according to afirst embodiment of the present invention.

FIG. 4 is a detailed flowchart of step S130 of the liquefied gastreatment method according to the first embodiment of the presentinvention.

FIG. 5 is a flowchart of a liquefied gas treatment method according to asecond embodiment of the present invention.

FIG. 6 is a detailed flowchart of step S230 of the liquefied gastreatment method according to the second embodiment of the presentinvention.

FIG. 7 is a flowchart of a liquefied gas treatment method according to athird embodiment of the present invention.

FIG. 8 is a detailed flowchart of step S330 of the liquefied gastreatment method according to the third embodiment of the presentinvention.

FIG. 9 is a flowchart of a liquefied gas treatment method according to afourth embodiment of the present invention.

FIG. 10 is a detailed flowchart of step S430 of the liquefied gastreatment method according to the fourth embodiment of the presentinvention.

BEST MODE

Hereinafter, an exemplary embodiment of the present invention will bedescribed in detail with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram of a liquefied gas treatment system inthe related art.

As illustrated in FIG. 1, a liquefied gas treatment system 1 in therelated art includes a liquefied gas storing tank 10, a source of demand20, a pump 30, and an electric heater 40. Hereinafter, in the presentspecification, liquefied gas may refer to all types of gas fuels, whichare generally stored in a liquid state, such as LNG or LPG, ethylene,and ammonia, and even when liquefied gas is not in a liquid state byheating or pressurization, the liquefied gas may be expressed asliquefied gas for convenience. This is also applicable to boil-off gas.

The liquefied gas treatment system 1 in the related art uses theelectric heater 40 receiving electrical energy to directly heatliquefied gas. However, the electrical energy necessary for driving theelectric heater 40 may be obtained only by driving a generator (notshown) by using fuel, so that a cost problem due to fuel consumption, anenvironmental pollution problem by exhaust gas generated during fuelcombustion, and the like may be generated.

FIG. 2 is a conceptual diagram of a liquefied gas treatment systemaccording to first to fourth embodiments of the present invention. InFIG. 2, a dotted line means a flow of transmission/reception of asignal.

As illustrated in FIG. 2, a liquefied gas treatment system 2 accordingto first to fourth embodiments of the present invention includes aliquefied gas storing tank 10, an engine 20, a pump 30, a heat exchanger50, a media supply device 60, a liquefied gas temperature sensor 70, amedia state detecting sensor 80, and a controller 90. In the embodimentsof the present invention, the liquefied gas storing tank 10, the engine20, the pump 30, and the like are denoted by the same reference numeralsas those of the respective elements of the liquefied gas treatmentsystem 1 in the related art for convenience, but do not necessarilydesignate the same elements.

The liquefied gas storing tank 10 stores liquefied gas to be supplied tothe source of demand 20. The liquefied storing tank 10 needs to storethe liquefied gas in a liquid state, and in this case, the liquefied gasstoring tank 10 may have a form of a pressure tank.

The liquefied gas storing tank 10 includes an external tank (not shown),an internal tank (not shown), and an insulation part. The external tank,which has a structure forming an outer wall of the liquefied gas storingtank 10, may be formed of steel, and may have a cross section shapedlike a polygon.

The internal tank is provided inside the external tank, and may beinstalled to be supported inside the external tank by a support (notshown). In this case, the support may be provided at a lower end of theinternal tank, and may be provided at a side surface of the internaltank in order to prevent the internal tank from moving in a horizontaldirection as a matter of course.

The internal tank may be formed of stainless steel, and may be designedso as to endure a pressure of 5 bars to 10 bars (for example, 6 bars).The liquefied gas contained inside the internal tank is evaporated andboil-off gas is generated, and thus an internal pressure of the internaltank may be increased. Therefore, the internal tank is designed so as toendure the predetermined pressure as described above.

The internal tank may have a baffle (not shown) therein. The bafflemeans a lattice-type plate, and when the baffle is installed, thepressure inside the internal tank is evenly distributed, therebypreventing a part of the internal tank from intensively receiving thepressure.

The insulation part may be provided between the internal tank and theexternal tank and may block external heat energy from being transferredto the internal tank. In this case, the insulation part may be in avacuum state. When the insulation part is formed to be in the vacuumstate, the liquefied gas storing tank 10 may more efficiently endure ahigh pressure compared to a general tank. For example, the liquefied gasstoring tank 10 may endure a pressure of 5 bars to 20 bars through thevacuum insulation part.

As described above, in the present exemplary embodiments, the pressuretank-type liquefied gas storing tank 10 including the vacuum-typeinsulation part, which is provided between the external tank and theinternal tank, is used, so that it is possible to minimize generation ofboil-off gas, and it is possible to prevent an occurrence of a problem,such as damage to the liquefied gas storing tank 10, even when theinternal pressure is increased.

The source of demand 20 receives the liquefied gas from the liquefiedgas storing tank 10. The source of demand 20 may be an engine driventhrough the liquefied gas to generate power, and for example, an MEGIengine or a dual fuel engine mounted in a vessel.

In a case where the source of demand 20 is a dual fuel engine, LNG,which is liquefied gas, is not mixed with oil to be supplied, but LNG oroil may be selectively supplied. The reason is that two materials havingdifferent combustion temperatures are prevented from being mixed andsupplied to prevent deterioration of efficiency of the engine.

In the engine, a piston (not shown) inside a cylinder (not shown)reciprocates by the combustion of the liquefied gas, so that a crankshaft (not shown) connected to the piston may be rotated, and a shaft(not shown) connected to the crank shaft may be rotated. Accordingly,when the engine is driven, a propeller (not shown) connected to theshaft is finally rotated, so that a ship body moves forward or backward.

In the present exemplary embodiments, the engine, which is the source ofdemand 20, may be an engine for driving the propeller, but may be anengine for generating electricity or other engines for generating poweras a matter of course. In other words, in the present embodiments, thetype of engine is not particularly limited. However, the engine may bean internal combustion engine for generating driving power by combustionof the liquefied gas.

A liquefied gas supply line 21 for transferring the liquefied gas may beinstalled between the liquefied gas storing tank 10 and the source ofdemand 20, and the pump 30, the heat exchanger 50, and the like may beprovided in the liquefied gas supply line 21, so that the liquefied gasmay be supplied to the source of demand 20.

In this case, a liquefied gas supply valve (not shown) may be installedin the liquefied gas supply line 21, so that the amount of liquefied gassupplied may be adjusted according to a level of opening the liquefiedgas supply valve.

Further, the liquefied gas temperature sensor 70 is provided in theliquefied gas supply line 21, and in the present exemplary embodiments,cascade control of calculating a target temperature of heat transfermedia supplying heat to the liquefied gas according to a temperature ofthe liquefied gas, appropriately changing the temperature of the heattransfer media heated through a media heater 63, and causing the heattransfer media to reach the target temperature may be implemented. Thiswill be described below.

The pump 30 is provided on the liquefied gas supply line 21 andpressurizes the liquefied gas discharged from the liquefied gas storingtank 10. The pump 30 may include a boosting pump 31 and a high pressurepump 32.

The boosting pump 31 may be provided on the liquefied gas supply line 21between the liquefied gas storing tank 10 and the high pressure pump 32or inside the liquefied gas storing tank 10, and may supply thesufficient amount of liquefied gas to the high pressure pump 32 toprevent cavitation of the high pressure pump 32. Further, the boostingpump 31 may take out the liquefied gas from the liquefied gas storingtank 10 and pressurize the liquefied gas to several to several tens ofbars, and the liquefied gas passing through the boosting pump 31 may bepressurized to 1 bar to 25 bars.

The liquefied gas stored in the liquefied gas storing tank 10 is in aliquid state. In this case, the boosting pump 31 may slightly increasethe pressure and the temperature of the liquefied gas by pressurizingthe liquefied gas discharged from the liquefied gas storing tank 10, andthe liquefied gas pressurized by the boosting pump 31 may still be in aliquid state.

The high pressure pump 32 pressurizes the liquefied gas discharged fromthe boosting pump 31 at a high pressure, so that the liquefied gas issupplied to the source of demand 20. The liquefied gas is dischargedfrom the liquefied gas storing tank 10 at a pressure withinapproximately 10 bars, and then is primarily pressurized by the boostingpump 31, and the high pressure pump 32 secondarily pressurizes theliquid-state liquefied gas pressurized by the boosting pump 31 to supplythe pressurized liquefied gas to the heat exchanger 50 to be describedbelow.

In this case, the high pressure pump 32 pressurizes the liquefied gas toa pressure demanded by the source of demand 20, for example, 200 bars to400 bars, to supply the pressurized liquefied gas to the source ofdemand 20, thereby enabling the source of demand 20 to generate powerthrough the liquefied gas.

The high pressure pump 32 pressurizes the liquid-state liquefied gasdischarged from the boosting pump 31 with a high pressure and mayphase-change the liquefied gas to be in a supercritical state having ahigher temperature and a higher pressure than a critical point. In thiscase, the temperature of the liquefied gas in the supercritical statemay be relatively higher than a critical temperature.

Otherwise, the high pressure pump 32 pressurizes the liquid-stateliquefied gas with a high pressure to change the liquid-state liquefiedgas to be in a supercooled liquid state. Here, the supercooled liquidstate of the liquefied gas means a state in which the pressure of theliquefied gas is higher than a critical pressure, and the temperature ofthe liquefied gas is lower than the critical temperature.

Specifically, the high pressure pump 32 pressurizes the liquid-stateliquefied gas discharged from the boosting pump 31 with a high pressureto 200 bars to 400 bars, in such a manner that the temperature of theliquefied gas is lower than the critical temperature, therebyphase-changing the liquefied gas to be in the supercooled liquid state.Here, the temperature of the liquefied gas in the supercooled state maybe −140° C. to −60° C., which is relatively lower than the criticaltemperature.

However, the high pressure pump 32 may be omitted when the source ofdemand 20 is a low pressure engine. In other words, when the source ofdemand 20 is a dual fuel engine, which is a lower pressure engine, theliquefied gas may be pressurized by the boosting pump 31, and may thenbe supplied to the source of demand 20 through the heat exchanger 50 tobe described below.

The heat exchanger 50 is provided on the liquefied gas supply line 21between the source of demand 20 and the pump 30, and heat-exchanges theliquefied gas supplied from the pump 30 with the heat transfer media andsupplies the heat-exchanged liquefied gas to the source of demand 20.The pump 30 for supplying the liquefied gas to the heat exchanger 50 maybe the high pressure pump 32, and the heat exchanger 50 may heat theliquefied gas in the supercooled liquid state or the supercritical statewhile maintaining 200 bars to 400 bars, which are pressures dischargedfrom the high pressure pump 32, convert the liquefied gas in thesupercooled liquid state or the supercritical state into the liquefiedgas in the supercritical state at 30° C. to 60° C., and then supply theconverted liquefied gas to the source of demand 20.

In the embodiment, the heat exchanger 50 may heat the liquefied gas byusing the heat transfer media supplied from the media heater 63 to bedescribed below. In this case, the heat transfer media may be glycolwater, and the glycol water is a fluid in which ethylene glycol is mixedwith water and may be heated by the media heater 63, cooled by the heatexchanger 50, and circulated along a media circulation line 64.

A temperature of the heat transfer media, which is heat-exchanged withthe liquefied gas in the heat exchanger 50 and then discharged, may bechanged according to the aforementioned phase change of the liquefiedgas of the high pressure pump 32. In other words, when the high pressurepump 32 phase changes the liquefied gas to be in the supercooled liquidstate and then supplies the phase changed liquefied gas to the heatexchanger 50, the heat transfer media may be cooled while heating theliquefied gas in the supercooled liquid state to 30° C. to 60° C., orwhen the high pressure pump 32 phase changes the liquefied gas to be inthe supercritical state and then supplies the phase changed liquefiedgas to the heat exchanger 50, the heat transfer media may be cooledwhile heating the supercritical state liquefied gas, which has a highertemperature than that of the supercooled liquid state, to a demandedtemperature of the source of demand 20. In this case, the heat transfermedia in a case of being heat exchanged with the liquefied gas in thesupercooled liquid state may be cooled to a lower temperature than thatof the heat transfer media in a case of being heat exchanged withliquefied gas in the supercritical state and then circulated into amedia tank 61.

When the liquefied gas discharged from the heat exchanger 50 does notreach or is excessively higher than the temperature demanded by thesource of demand 20, in the present embodiment, a target temperature ofthe heat transfer media is calculated according to the measuredtemperature of the liquefied gas, and the heat transfer media are heatedto the target temperature of the heat transfer media by causing at leasta part of the heat transfer media to bypass, adjusting a flow rate ofthe heat transfer media by a media pump 62, or adjusting a quantity ofheat sources supplied to the media heater 63, thereby controlling thetemperature of the liquefied gas to be appropriate to the demandedtemperature of the liquefied gas of the source of demand 20. The cascadecontrol will be described below.

However, when the temperature of the heat transfer media, which isheat-exchanged with the liquefied gas in the heat exchanger 50, is lowerthan a freezing temperature of water at a specific pressure, waterincluded in the heat transfer media is frozen, so that the heat transfermedia are separated into water and ethylene glycol. However, in theembodiment, the temperature of the heat transfer media is detected in ordownstream of the heat exchanger 50, and a heating flow of the heattransfer media is controlled through the detected temperature, therebypreventing water from being separated from the heat transfer media.

The media supply device 60 supplies the heat transfer media to the heatexchanger 50. The media supply device 60 includes the media tank 61, themedia pump 62, the media heater 63, the media circulation line 64, abranch line 65, a heat source supply line 66, and a flow rate adjustingvalve 67.

The media tank 61 stores the heat transfer media. The heat transfermedia may be glycol water as described above, and the media tank 61 maystore the heat transfer media at a temperature at which cracking (aphenomenon in which water and ethylene glycol are separated due to aphase change of water) of the glycol water may be prevented.

The media pump 62 is provided at a downstream of the media tank 61, sothat the predetermined amount of heat transfer media may flow into themedia heater 63 from the media tank 61 by the media pump 62. Further,the heat exchanger 50 is connected to an upstream of the media tank 61,so that the heat transfer media, which is cooled after supplying heat tothe liquefied gas, may flow into the media tank 61 again.

The media tank 61, the media pump 62, the media heater 63, and the heatexchanger 50 may be connected with each other by the media circulationline 64. In other words, the heat transfer media may move sequentiallyfrom the media tank 61 through the media pump 62 and the media heater 63to the heat exchanger 50 while moving along the media circulation line64 to be heated or cooled.

The media pump 62 supplies the heat transfer media stored in the mediatank 61 to the media heater 63. The media pump 62 may be provided at thedownstream of the media tank 61, and the number of media pumps 62 may beplural, so that when any one of the media pumps 62 is damaged, the heattransfer media may be smoothly supplied through another media pump 62.

Driving of the media pump 62 may be controlled by the controller 90 tobe described below to control a flow rate of the heat transfer mediasupplied to the media heater 63. A driving speed (RPM), a pressure, andthe like of the media pump 62 may be changed by the controller 90, whichmeans that a flow rate of the heat transfer media flowing into the mediaheater 63 is finally changed.

In the present embodiment, it is possible to decrease a flow rate of thecirculated liquefied gas by minimizing the operation of the media pump62 within a limit in which the heated liquefied gas is appropriate tothe demanded temperature of the liquefied gas of the source of demand 20when the liquefied gas is heated by the heat exchanger 50, it ispossible to improve efficiency of the media pump 62, and the like, anddecrease energy consumption.

The media heater 63 heats the heat transfer media discharged from themedia tank 61 and then supplies the heated heat transfer media to theheat exchanger 50. The media heater 63 heats the heat transfer media ata predetermined temperature, so that the heat transfer media may enablethe heat exchanger 50 to supply sufficient heat to the liquefied gas.

The media heater 63 may heat the heat transfer media by using electricalenergy. However, the mediate heater 63 may use steam in the presentembodiment. In other words, the heat source supply line 66 for supplyinga heat source is connected to the media heater 63, and the heat sourcesupply line 66 supplies steam generated by a boiler (not shown) to themedia heater 63, the steam supplies heat to the heat transfer media, andthe heat transfer media cool the steam, so that the heat transfer mediamay be heated, and the steam may be condensed to condensed water.

In this case, the condensed water may flow into the boiler again througha condensed water tank (not shown), be changed to steam, and then flowinto the media heater 63 again, and the heat transfer media heated bythe steam may be discharged from the media heater 63 to flow into theheat exchanger 50.

The media circulation line 64 is connected from the media heater 63 tothe heat exchanger 50 to circulate the heat transfer media. The heattransfer media may be heated in the media heater 63 while beingcirculated along the media circulation line 64, and may be cooled by theliquefied gas in the heat exchanger 50.

Further, the media circulation line 64 connects the media tank 61, themedia pump 62, the media heater 63, and the heat exchanger 50 so as tocause the heat transfer media to be circulated. Accordingly, in thepresent embodiment, the heat transfer media are re-used, therebyimproving efficiency.

The branch line 65 causes at least some of the heat transfer media to bebranched from the media circulation line to bypass the media heater 63.The branch line 65 may be branched at an upstream point of the mediaheater 63 on the media circulation line 64 to be joined at a downstreampoint of the media heater 63.

The heat transfer media bypassing the media heater 63 through the branchline 65 and the heat transfer media flowing into the media heater 63through the media circulation line 64 without flowing into the branchline 65 may be joined at the downstream of the media heater 63, and inthis case, the temperature of the heat transfer media bypassing themedia heater 63 may be lower than the temperature of the heat transfermedia heated by the media heater 63.

In this case, when a flow rate of the heat transfer media bypassing themedia heater 63 is adjusted, the temperature of the heat transfer mediaflowing into the heat exchanger 50 may be effectively controlled. Inother words, in the present embodiment, some of the heat transfer mediabypasses the media heater 63 and is then joined, so that the temperatureof the heat transfer media may be changed.

The branch line 65 may include a bypass adjusting valve 651. A degree ofopening of the bypass adjusting valve 651 is controlled by thecontroller 90 to be described below, thereby adjusting a flow rate ofthe heat transfer media flowing into the branch line 65. The bypassadjusting valve 651 may be a 2-way valve provided on the branch line 65,and a detailed flow of the heat transfer media moving through the branchline 65 will be described below.

The heat source supply line 66 supplies a heat source to the mediaheater 63. In this case, the heat sources, which heat the heat transfermedia and cause the heated heat transfer media to heat the liquefiedgas, may be steam. In other words, the heat source supply line 66 may bea steam supply line. A heat source supply valve 661 may be provided onthe heat source supply line 66.

The heat source supply valve 661 may adjust a degree of opening of theheat source supply line 66, and the amount of steam flowing along theheat source supply line 66 is controlled by the heat source supply valve661, and a temperature of the heat transfer media heated by the mediaheater 63 may be changed. The heat source supply valve 661 is controlledby the controller 90, so that it is possible to prevent a crackingphenomenon in which the heat transfer media are gasified so that amaterial included in the heat transfer media (water in a case where theheat transfer media are glycol water) is separated.

The flow rate adjusting valve 67 is provided on the media circulationline 64 and adjusts a flow rate of the heat transfer media flowing intothe media heater 63. The flow rate adjusting valve 67 may be provided atthe downstream of the media pump 62, and a degree of opening thereof maybe controlled by the controller 90, thereby changing the flow rate ofthe heat transfer media circulating through the media circulation line64.

In this case, a media flow rate sensor 671 for measuring a flow rate ofthe heat transfer media flowing into the media heater 63 may be providedat one side of the flow rate adjusting valve 67. The media flow ratesensor 671 may be provided on the media circulation line 64. The mediaflow rate sensor 671 measures a flow rate of the heat transfer mediacirculating in the media circulation line 64 and transmits the measuredflow rate to the controller 90, thereby causing the controller 90 toappropriately adjust the degree of opening of the flow rate adjustingvalve 67.

The liquefied gas temperature sensor 70 is provided on the liquefied gassupply line 21 and measures a temperature of the liquefied gas. Theliquefied gas temperature sensor 70 may be provided between the heatexchanger 50 and the source of demand 20 on the liquefied gas supplyline 21 and may measure the temperature of the liquefied gas after beingheated by the heat transfer media in the heat exchanger 50.

The measured temperature of the liquefied gas may be compared with thedemanded temperature of the liquefied gas of the source of demand 20 bythe controller 90 to be described below, and a target temperaturecalculator 91 of the controller 90 may calculate the target temperatureof the heat transfer media through the comparison. This will bedescribed below.

The media state detecting sensor 80 is provided on the media circulationline 64 and measures a state of the heat transfer media. The media statedetecting sensor 80 may include a first media state detecting sensor 81for detecting a temperature of the heat transfer media at the downstreamof the media heater 63, and a second media state detecting sensor 82 fordetecting the temperature of the heat transfer media downstream of or inthe heat exchanger 50.

The first media state detecting sensor 81 is provided at the downstreamof the media heater 63 on the media circulation line 64 and may measurea temperature of the heat transfer media heated by the media heater 63.The heat transfer media, detected by the first media state detectingsensor 81, mean the heat transfer media after being heated by the mediaheater 63 and include heat to be supplied to the liquefied gas by theheat exchanger 50.

When the temperature of the heat transfer media detected by the firstmedia state detecting sensor 81 is low, the temperature of the liquefiedgas, which is heated by receiving heat from the heat transfer media bythe heat exchanger 50, is also low, but when the temperature of the heattransfer media detected by the first media state detecting sensor 81 ishigh, the temperature of the liquefied gas discharged from the heatexchanger 50 may also be high.

In other words, the temperature detected by the first media statedetecting sensor 81 may be a value, through which the temperature of theliquefied gas supplied to the source of demand 20 from the heatexchanger 50 is predictable, and in the present embodiment, thetemperature of the heat transfer media may be changed so that thetemperature of the liquefied gas corresponds to the demanded temperatureof the source of demand 20 through the detected temperature. Thetemperature of the heat transfer media may be adjusted by theaforementioned branch line 65, media pump 62, and heat source supplyvalve 661.

The first media state detecting sensor 81 may be provided at an upstreamof a point at which the heat transfer media bypassing on the mediacirculation line 64 through the branch line 65 are joined. In this case,the first media state detecting sensor 81 detects a temperature of theheat transfer media discharged from the media heater 63, and thedetected temperature may be used so as to prevent the crackingphenomenon from occurring in the heat transfer media by gasification ofthe heat transfer media.

The first media state detecting sensor 81 may also be provided at adownstream of the point at which the heat transfer media bypassing onthe media circulation line 64 through the branch line 65 are joined. Inthis case, a difference between the temperatures detected by the firstmedia state detecting sensor 81 and the second media state detectingsensor 82 means calories supplied to the liquefied gas from the heatexchanger 50.

The second media state detecting sensor 82 may be provided at thedownstream of the heat exchanger 50 on the media circulation line 64 orinside the heat exchanger 50, to detect a temperature of the heattransfer media. The temperature of the heat transfer media detected bythe second media state detecting sensor 82 means a temperature of theheat transfer media cooled by the liquefied gas in the heat exchanger50.

When the temperature, detected by the second media state detectingsensor 82, is excessively low, a material (for example, water) includedin the heat transfer media may be coagulated. Therefore, in the presentembodiment, the temperature detected by the second media state detectingsensor 82 is compared with a coagulation prevention reference value,thereby preventing an icing phenomenon of the heat transfer media.

Further, the media state detecting sensor 80 may detect a differencebetween the temperatures of the heat transfer media at front and rearends of the heat exchanger 50 by using the first media state detectingsensor 81 and the second media state detecting sensor 82. In this case,the difference between the temperatures of the heat transfer media istransmitted to the controller 90, and the controller 90 causes thedifference between the temperatures of the heat transfer media to be apredetermined value or more, so that the liquefied gas may besufficiently heated to the demanded temperature of the liquefied gas ofthe source of demand 20. In this case, the controller 90 may improveefficiency of the media pump 62 by decreasing the flow rate of the heattransfer media within a limit in which the difference between thetemperatures of the heat transfer media is equal to or greater than thepredetermined value.

The controller 90 changes the flow rate of the heat transfer mediaflowing into the media heater 63 or the calories supplied to the heattransfer media by the media heater 63. Hereinafter, control of thecontroller 90 will be described for each embodiment.

In a first embodiment of the present invention, the controller 90 maychange a flow rate of the heat transfer media or calories supplied tothe heat transfer media based on the measured temperature of theliquefied gas. Specifically, the controller 90 may include the targettemperature calculator 91 for calculating a target temperature of theheat transfer media by using the measured temperature of the liquefiedgas, and may change a flow rate, and the like of the heat transfer mediabased on the target temperature of the heat transfer media.

In other words, the controller 90 may directly control the flow rate andthe like of the heat transfer media by using the measured temperature ofthe liquefied gas, or may calculate a target temperature of the heattransfer media based on the measured temperature of the liquefied gasand then control the flow rate of the heat transfer media by using thetarget temperature of the heat transfer media. The latter is referred toas cascade control.

In this case, the target temperature calculator 91 may calculate thetarget temperature of the heat transfer media through PID control usinga deviation between the demanded temperature of the liquefied gas of thesource of demand 20 and the measured temperature of the liquefied gas.The PID control is to output the temperature of the heat transfer mediaby using a proportional term of a deviation, an integral term meaning anaccumulation value of deviations, and a derivative term meaning adifference between a current deviation and a past deviation, and adetailed calculation formula of the PID control is a general matter, sothat a detailed description thereof will be omitted.

The target temperature calculator 91 may calculate the targettemperature of the heat transfer media by using the measure temperatureof the liquefied gas at a predetermined time interval or in real timethrough the PID control, and the target temperature of the heat transfermedia may be transmitted to the controller 90.

For example, when the liquefied gas is LNG and the source of demand 20is the engine, and the demanded temperature of the liquefied gas of thesource of demand 20 is 45° C. and the measured temperature of thecurrent liquefied gas is 50° C., the target temperature of the heattransfer media may be calculated based on 5° C. which is a deviationbetween the measured temperature of the current liquefied gas and thedemanded temperature of the liquefied gas of the source of demand 20.For example, the target temperature of the heat transfer media iscalculated as 60° C., and whether the temperature of the heat transfermedia reaches the target temperature may be identified by the mediastate detecting sensor 80 (particularly, the first media state detectingsensor 81).

As the temperature of the heat transfer media is close to the targettemperature, the measured temperature of the liquefied gas may bechanged. When the temperature of the heat transfer media is close to 60°C. to be decreased, the measured temperature of the liquefied gas may be43° C., which is lower than 45° C. In this case, the target temperaturecalculator 91 re-calculates the temperature of the heat transfer mediathrough the PID control and may cause the temperature of the heattransfer media to be, for example, 62° C. As described above,considering that the temperature of the liquefied gas is changed againaccording to the change in the temperature of the heat transfer media,the target temperature calculator 91 may calculate the targettemperature of the heat transfer media at a predetermined time intervalor in real time, and as a result, the liquefied gas may converge on thedemanded temperature of the liquefied gas of the source of demand 20.

However, the target temperature of the heat transfer media may bepositioned within a predetermined temperature range of the heat transfermedia. For example, the temperature range of the heat transfer media is45° C. to 85° C. and may be a value set by an input.

Otherwise, the target temperature calculator 91 may calculate the targettemperature of the heat transfer media based on the measured temperatureof the liquefied gas by using a demanded temperature range of theliquefied gas of the source of demand 20 and the temperature range ofthe heat transfer media. In this case, each temperature range may be apredetermined value.

For example, in a case where a temperature range of the demandedtemperature of the liquefied gas of the source of demand 20 is 40° C. to60° C. (an interval of 20° C.), and a temperature range of the heattransfer media is 45° C. to 85° C. (an interval of 40° C.), thetemperature of the heat transfer media may correspond to 51° C. by arange proportional conversion when the measured temperature of theliquefied gas is 43° C. (The measured temperature is higher than thelowest temperature of the temperature range by 3° C., and a temperaturehigher than the lowest temperature by 6° C. is applied when reflectingto the temperature range of the heat transfer media.). Thus, the targettemperature calculator 91 may also calculate the target temperature ofthe heat transfer media through the proportional conversion consideringthe temperature range.

The controller 90 may control the flow rate of the heat transfer mediasupplied to the media heater 63 from the media pump 62 by controllingthe driving of the media pump 62 based on the target temperature of theheat transfer media calculated by the target temperature calculator 91,or may adjust the flow rate of the heat transfer media flowing into thebranch line 65 through the bypass adjusting valve 651 provided on thebranch line 65.

Specifically, when the target temperature is higher than the currenttemperature of the heat transfer media, the controller 90 may increasecalories, which the heat transfer media may supply to the liquefied gasin the heat exchanger 50, by supplying the large amount of heat transfermedia to the media heater 63 by increasing RPM, and the like of themedia pump 62, or decreasing the flow rate of the heat transfer mediabypassing to the branch line 65. When the target temperature is lowerthan the current temperature of the heat transfer media, controlopposite to the aforementioned control may be performed as a matter ofcourse.

In this case, in a case of controlling the media pump 62, targetcalories of the heat transfer media may be calculated considering thetarget temperature calculated by the target temperature calculator 91,the flow rate of the heat transfer media detected by the media flow ratesensor 671, and a flow rate of the liquefied gas (which may be detectedby a separate liquefied gas flow rate sensor (not shown)) together, andthe media pump 62 may also be controlled according to the targetcalories. The reason is to prepare a case where the temperature of theheat transfer media heated by the heat sources by the media heater 63 isuniform regardless of the flow rate.

In other words, even though the heat transfer media reaches the targettemperature by the media heater 63 to flow into the heat exchanger 50,the liquefied gas may not reach the demanded temperature of theliquefied gas of the source of demand 20. The reason is that the flowrate of the heat transfer media is insufficient.

Accordingly, the target temperature calculator 91 may calculate thetarget calories of the heat transfer media considering the flow rate ofthe liquefied gas and the flow rate of the heat transfer media, and thedriving of the media pump 62 may be controlled based on the targetcalories of the heat transfer media.

In addition, the controller 90 may change a heating temperature of theheat transfer media by controlling the amount of heat sources, which themedia heater 63 supplies to the heat transfer media, by adjusting adegree of opening of the heat source supply valve 661 provided in theheat source supply line 66. In other words, the controller 90 may adjusta degree of opening of the heat source supply valve 661 so as toincrease the amount of heat sources supplied when the target temperatureis higher than the current temperature of the heat transfer media, andto decrease the amount of heat sources when the target temperature islower than the current temperature of the heat transfer media.

Further, the controller 90 may return at least some of the heat transfermedia, which flows from the media pump 62 to the media heater 63, to themedia tank 61 or the media pump 62, thereby changing the amount of heattransfer media flowing into the media heater 63. The controller 90 inthe present embodiment is not limited to the aforementioned contents,and any control may be adopted as long as the control may change theflow rate of the heat transfer media supplied to the media heater 63.

As described above, in the present embodiment, the target temperature ofthe heat transfer media is calculated by using the measured temperatureof the liquefied gas, and the flow of the heat transfer media iscontrolled by the calculated target temperature of the heat transfermedia, thereby efficiently heating the liquefied gas to have thedemanded temperature of the liquefied gas of the source of demand 20.

In a second embodiment of the present invention, the controller 90 setsa coagulation prevention reference value for preventing the heattransfer media from being coagulated (the material included in the heattransfer media may be coagulated), and changes the flow rate of the heattransfer media flowing into the media heater 63 or the calories suppliedto the heat transfer media by the media heater 63, based on a statevalue of the heat transfer media by the media state detecting sensor 80and the coagulation prevention reference value.

The heat transfer media may be glycol water as described above and mayinclude water. When the heat transfer media are supercooled to apredetermined temperature or low during a process of being cooled by theliquefied gas in the heat exchanger 50, water included in the heattransfer media is frozen. As a result, the heat transfer media may notbe used.

Accordingly, the controller 90 may previously set the coagulationprevention reference value for preventing the water included in the heattransfer media from being frozen. The coagulation prevention referencevalue may be, for example, 30° C., but is not limited thereto, and maybe changed according to a pressure or a flow rate of the heat transfermedia or the liquefied gas.

The controller 90 may change the flow rate of the heat transfer mediaand the like so that the state value of the heat transfer media is equalto or greater than the coagulation prevention reference value. In thiscase, the state value of the heat transfer media means a state value bythe second media state detecting sensor 82, that is, a temperature ofthe heat transfer media cooled in the heat exchanger 50.

The controller 90 may prevent an icing phenomenon that water included inthe heat transfer media is frozen by causing the temperature of the heattransfer media cooled in the heat exchanger 50 to be equal to or greaterthan the coagulation prevention reference value.

To this end, the controller 90 may cause the state value of the heattransfer media to be equal to or greater than the coagulation preventionreference value by changing the flow rate of the heat transfer mediasupplied to the media heater 63 or the calories supplied to the heattransfer media by controlling the bypass adjusting valve 651 provided inthe branch line 65, controlling the driving of the media pump 62, orcontrolling the heat source supply valve 661.

Specifically, when the temperature of the heat transfer media is lowerthan the coagulation prevention reference value, the controller 90 mayincrease the temperature of the heat transfer media or the calories bydecreasing a degree of opening of the bypass adjusting valve 651 (theheat transfer media have a sufficient temperature when the heat transfermedia bypassing the media heater 63 are joined with the heat transfermedia heated by the media heater 63, thereby preventing the icingphenomenon), increasing RPM of the media pump 62 (when it is assumedthat the media heater 63 supplies sufficient heat resources, the icingphenomenon is prevented by increasing the total calories which the heattransfer media are receivable), and increasing a degree of opening ofthe heat source supply valve 661.

Accordingly, in the present embodiment, even though the heat transfermedia are cooled by the liquefied gas in the heat exchanger 50, thetemperature of the heat transfer media or the calories are sufficientlyincreased so as to prevent the icing phenomenon from being generated, sothat the heat transfer media may be smoothly circulated.

However, when the heat transfer media flowing into the heat exchanger 50fail to be discharged along the media circulation line 64 from the heatexchanger 50 due to an unexpected reason, the heat transfer media arecooled by the liquefied gas continuously flowing into the heat exchanger50, so that the icing phenomenon may be generated.

Accordingly, in the present embodiment, the present invention mayfurther include a media discharge line 93 for preventing the icingphenomenon from being generated in the heat transfer media flowing intothe heat exchanger 50 when the circulation of the heat transfer media isnot smooth, preventing the heat exchanger 50 from being damaged due tothe heat transfer media in which the icing phenomenon is generated, orpreventing a system from being stopped.

The media discharge line 93 is connected to the heat exchanger 50 todischarge the heat transfer media flowing into the heat exchanger 50 tothe outside. When the media are normally circulated by theaforementioned control of the controller 90, the icing phenomenon is notgenerated in the heat transfer media in the heat exchanger 50. However,when the heat transfer media fail to be discharged and remain in theheat exchanger 50 due to generation of a problem in the mediacirculation, the icing phenomenon may be generated in the heat transfermedia by cold energy of the liquefied gas continuously supplied to theheat exchanger 50.

Accordingly, in the present embodiment, the media discharge line 93 isprovided at one side of the heat exchanger 50, and when it is detectedthat a problem is generated in the media circulation, the heat transfermedia remaining in the heat exchanger 50 may be discharged to theoutside.

In this case, a media discharge valve 94 may be further provided on themedia discharge line 93. The media discharge valve 94 is provided on themedia discharge line 93, and a degree of opening of the media dischargevalve 94 may be adjusted based on the state value of the heat transfermedia by the media state detecting sensor 80 (particularly, the secondmedia state detecting sensor 82), and the coagulation preventionreference value.

The second media state detecting sensor 82 is provided downstream of orin the heat exchanger 50, so that when the temperature of the heattransfer media cooled in the heat exchanger 50 is compared with thecoagulation prevention reference value, and the temperature of the heattransfer media is lower than the coagulation prevention reference value,a degree of opening of the media discharge valve 94 is increased,thereby discharging the heat transfer media to the media discharge line93.

When the temperature of the heat transfer media is so low there is arisk of system stoppage due to the icing phenomenon, the degree ofopening of the media discharge valve 94 may be controlled, because thereis a problem in heating the liquefied gas when the heat transfer mediaare discharged along the media discharge line 93 by the media dischargevalve 94.

The media discharge line 93 may transmit the heat transfer mediadischarged from the heat exchanger 50 to a separate media processingfacility (not shown), and in this case, the separate media processingfacility may throw away the heat transfer media discharged from the heatexchanger 50, or heat and cause the heat transfer media to be dischargedfrom the heat exchanger 50 flow into the circulation line 64 again.

Otherwise, the media discharge line 93 has one end connected to the heatexchanger 50, and the other end connected to the media tank 61, tocollect the heat transfer media flowing into the heat exchanger 50 tothe media tank 61. Accordingly, the heat transfer media may bere-circulated along the media tank 61, the media pump 62, and the mediaheater 63 to be used.

Otherwise, the media discharge line 93 has one end connected to the heatexchanger 50, and the other end connected in or upstream of the mediapump 62, to supply the heat transfer media flowing into the heatexchanger 50 to the media pump 62. In this case, similar to theaforementioned case, the heat transfer media may be re-used.

However, the heat transfer media discharged along the media dischargeline 93 may have a low temperature to have a high risk of the icingphenomenon, so that the media discharge line 93 includes an auxiliaryheater (not shown) and heats the heat transfer media, and then suppliesthe heated heat transfer media to the media tank 61 or the media pump62, thereby smoothly using the heat transfer media.

The media discharge line 93 may further include a temporary mediastoring tank 95. The temporary media storing tank 95 may temporarilystore the low-temperature heat transfer media discharged from the heatexchanger 50, heat the temporarily stored heat transfer media throughexternal heat sources (air and the like), and then supply the heatedheat transfer media to the media tank 61 or the media pump 62.

The media discharge line 93 may cause the heat transfer media to bedischarged from the heat exchanger 50 be supplied to the media tank 61or the media pump 62 by passing through the temporary media storing tank95, or cause the heat transfer media to be discharged from the heatexchanger 50 be supplied to the media tank 61 or the media pump 62 bybypassing the temporary media storing tank 95.

To this end, the media discharge line 93 is divided from an upstream ofthe temporary media storing tank 95 to be connected to the temporarymedia storing tank 95, or the media tank 61 or the media pump 62, andthe passing or the bypassing of the temporary media storing tank 95 maybe controlled by a temporary storage valve (not shown) provided in themedia discharge line 93. In this case, the temporary storage valve maybe provided at a branch point of the media discharge line 93 at theupstream of the temporary media storing tank 95.

When the heat transfer media are discharged along the media dischargeline 93, a water level of the media tank 61 may be maintained in areduced state. Accordingly, the heat transfer media stored in thetemporary media storing tank 95 may be first supplied to the media pump62.

Otherwise, the heat transfer media stored in the media tank 61 and thetemporary media storing tank 95 may simultaneously flow into the mediapump 62, or separately flow into the media pump 62.

As described above, in the present embodiment, it is possible to preventthe problems of damage to the heat exchanger 50, stoppage of the systemdue to the icing phenomenon and the like by changing the flow rate ofthe heat transfer media flowing into the media heater 63 or the caloriessupplied to the heat transfer media by the media heater so as to preventthe generation of the icing phenomenon in the heat transfer media cooledin the heat exchanger 50, and discharging the heat transfer mediaremaining inside the heat exchanger 50 to the media discharge line 93when abnormality is generated in the media circulation.

In a third embodiment of the present invention, the controller 90 sets agasification prevention reference value for preventing the heat transfermedia from being gasified (the material included in the heat transfermedia may be gasified), and changes the flow rate of the heat transfermedia flowing into the media heater 63 or the calories supplied to theheat transfer media by the media heater 63 based on the state value ofthe heat transfer media by the media state detecting sensor 80 and thegasification prevention reference value.

The heat transfer media may be glycol water as described in the secondembodiment and include water. Therefore, when the heat transfer mediaare heated by the media heater 63, water included in the heat transfermedia is evaporated and leaks. As a result, it is impossible to use theheat transfer media.

Accordingly, the controller 90 may cause a temperature, which is a statevalue of the heat transfer media, to be equal to or lower than atemperature set as the gasification prevention reference value. In thiscase, the gasification prevention reference value, which is atemperature for preventing water included in the heat transfer mediafrom being gasified, may be 95° C., which is changeable.

In this case, the media state detecting sensor 80 means the first mediastate detecting sensor 81, and the state value of the heat transfermedia means the temperature of the heat transfer media heated by themedia heater 63. The temperature of the heat transfer media may bechanged according to a heat source supplied to the heat transfer mediaby the media heater 63, and when the heat transfer media receive therelatively large amount of calories for each unit flow rate by the heatsource supplied to the media heater 63 according to the decrease in theflow rate of the heat transfer media, a cracking phenomenon, in whichthe temperature of the heat transfer media is increased so that water isseparated, may be generated.

In order to prevent the generation of the cracking phenomenon, thecontroller 90 may control the bypass adjusting valve 651, control thedriving of the media pump 62, or control the degree of opening of theheat source supply valve 661 so that the temperature of the heattransfer media discharged from the media heater 63 is lower than thetemperature set as the gasification prevention reference value.

Specifically, when the temperature of the heat transfer media is equalto or higher than the gasification prevention reference value, thecontroller 90 may prevent the generation of the cracking phenomenon byincreasing a degree of opening of the bypass adjusting valve 651 (thecracking phenomenon is prevented at a joint flow of the heat transfermedia bypassing the media heater 63 and the heat transfer media passingthrough the media heater 63), increasing RPM of the media pump 62 (whenthe calories supplied to the media heater 63 are uniform, the heattransfer media receive relatively smaller calories for each unit flowrate by the supplied calories of the media heater 63, thereby preventingthe cracking phenomenon), and decreasing the temperature of the heattransfer media discharged from the media heater 63 and moving to theheat exchanger 50 by decreasing the degree of opening of the heat sourcesupply valve 661.

Further, in the present embodiment, the present invention may furtherinclude a phase separator 92. The phase separator 92 is provided at thedownstream of the media heater 63 of the media circulation line 64, anddetects the gasification of the heat transfer media (or the gasificationof the material included in the heat transfer media), discharges thegasified heat transfer media (or the material included in the heattransfer media) to the outside, and causes the remaining heat transfermedia to flow into the heat exchanger 50 through the media circulationline 64.

The phase separator 92 may be a gas-liquid separator, and may separateevaporated gas and supply the liquid-state heat transfer media to theheat exchanger 50 for the heat transfer media in which the crackingphenomenon is generated. The phase separator 92 may be provided at adownstream of a point, at which the branch line 65 is connected to themedia circulation line 64, at the downstream of the media heater 63.

In other words, the aforementioned control of the controller 90 isprovided for the purpose of preventing the cracking, and the phaseseparator 92 is provided for the purpose of preparing a case where thecracking is generated. In this case, since the material, discharged fromthe phase separator 92, may be steam, the material may be discharged tothe air without separate purification.

As described above, the controller 90 may maintain the temperature ofthe heat transfer media heated by the media heater 63 to be lower thanthe gasification prevention reference value, so that it is possible toprevent the cracking of the heat transfer media, and even though thecracking is generated, the controller 90 may remove a gaseous materialthrough the phase separator 92 to implement smooth heating of theliquefied gas.

In a fourth embodiment of the present invention, the controller 90causes the measured temperature of the liquefied gas to be equal to orgreater than the demanded temperature of the source of demand 20, anddecreases (minimizes) the flow rate of the heat transfer media flowinginto the media heater 63. The measured temperature of the liquefied gasis a value measured by the liquefied gas temperature sensor 70 and meansa temperature of the liquefied gas heated in the heat exchanger 50.

The controller 90 may improve efficiency of the media pump 62 bydecreasing a circulation flow rate of the heat transfer media within arange in which the liquefied gas meets the demanded temperature of thesource of demand 20.

As the flow rate of the heat transfer media circulating along the mediacirculation line 64 is large, efficiency of the media pump 62, and thelike provided in the media circulation line 64 may be decreased.Accordingly, the controller 90 may decrease the flow rate of the heattransfer media flowing into the media heater 63 as compared to theearlier case, but in order to prevent the heating temperature of theliquefied gas from being decreased more than needed due to the decreasein the flow rate of the heat transfer media, the controller 90 may causethe measured temperature of the liquefied gas to meet the demandedtemperature of the source of demand 20.

The controller 90 may control the flow rate of the heat transfer mediasupplied to the media heater 63 from the media pump 62 by controllingthe driving of the media pump 62, and particularly, may adjust RPM ofthe media pump 62. Further, the controller 90 may control the flow rateof the heat transfer media by adjusting the degree of opening of theflow rate adjusting valve 67 provided at the downstream of the mediapump 62 on the media circulation line 64.

The controller 90 may decrease the flow rate of the heat transfer mediabased on the measured temperature of the liquefied gas, or may decreasethe flow rate of the heat transfer media while causing a differencebetween the temperatures of the heat transfer media at the front andrear ends of the heat exchanger 50, detected by the media statedetecting sensor 80, to be equal to or greater than a predeterminedvalue.

The difference between the temperatures of the heat transfer media atthe front and rear ends of the heat exchanger 50 means a differencebetween a temperature measured by the first media state detecting sensor81 and a temperature measured by the second media state detecting sensor82, and may mean calories supplied to the liquefied gas. In other words,when the difference between the temperatures of the heat transfer mediaat the front and rear ends of the heat exchanger 50 is large, it meansthat the liquefied gas receives the large amount of heat. Accordingly,the controller 90 may cause the difference between the temperatures ofthe heat transfer media to be equal to or greater than the predeterminedvalue so that the liquefied gas may be sufficiently heated to thedemanded temperature of the liquefied gas of the source of demand 20,and the controller 90 may decrease the flow rate of the heat transfermedia.

In this case, the predetermined value for the comparison with thedifference between the temperatures of the heat transfer media at thefront and rear ends of the heat exchanger 50 may be changed according tothe flow rate of the liquefied gas, so that the controller 90 mayconsider the flow rate of the heat transfer media together with thedifference in the temperatures of the heat transfer media. The flow rateof the heat transfer media may be detected by the aforementioned mediaflow rate sensor 671,

As described above, in the present embodiment, the liquefied gas isheated to the demanded temperature of the liquefied gas of the source ofdemand 20 considering the flow rate of the heat transfer media and thedifference in the temperatures at the front and rear ends of the heatexchanger 50, and the flow rate of the heat transfer media flowing intothe media heater 63 is decreased, thereby improving efficiency of themedia pump 62.

Hereinafter, a liquefied gas treatment method according to first tofourth embodiments of the present invention will be described in detailwith reference to FIGS. 3 to 10. The liquefied gas treatment methodaccording to the first to fourth embodiments of the present inventionmay be implemented by the liquefied gas treatment system 2 according tothe first to fourth embodiments of the present invention.

FIG. 3 is a flowchart of a liquefied gas treatment method according to afirst embodiment of the present invention.

As illustrated in FIG. 3, the liquefied gas treatment method accordingto the first embodiment of the present invention includes measuring atemperature of liquefied gas supplied to the source of demand 20 (S110),calculating a target temperature of the heat transfer media based on themeasured temperature of the liquefied gas (S120), and changing a flowrate of the heat transfer media flowing into the media heater 63 orcalories applied to the heat transfer media by the media heater 63according to the target temperature of the heat transfer media (S130).

In step S110, the temperature of the liquefied gas supplied to thesource of demand 20 is measured. The temperature of the liquefied gasmay be measured by the liquefied gas temperature sensor 70, and in thiscase, the measured temperature of the liquefied gas, which is thetemperature of the liquefied gas between the heat exchanger 50 and thesource of demand 20, may be the temperature of the liquefied gas heatedby the heat exchanger 50.

When the temperature of the liquefied gas measured in step 110 is notappropriate for a demanded temperature of the liquefied gas of thesource of demand 20, the controller 90 may control the flow rate of theheat transfer media to be supplied to the media heater 63 or the flowrate supplied to the heat transfer media by the media heater 63.

In step S120, the target temperature of the heat transfer media iscalculated based on the measured temperature of the liquefied gas. Thetarget temperature of the heat transfer media may be calculated by PIDcontrol through a deviation between the measured temperature of theliquefied gas and the demanded temperature of the liquefied gas of thesource of demand 20. Otherwise, the target temperature of the heattransfer media may be calculated through a proportional conversion usinga temperature range of the demanded temperature of the liquefied gas ofthe source of demand 20 and a temperature range of the heat transfermedia. The calculation of the target temperature has been described inthe description of the target temperature calculator 91, so that adetailed description thereof will be omitted.

As described above, in the present embodiment, it is possible toimplement cascade control of calculating the target temperature of theheat transfer media based on the measured temperature of the liquefiedgas and then controlling a flow of the heat transfer media based on thetarget temperature. In the present embodiment, step S120 may be omitted,and the flow rate of the heat transfer media and the like may bedirectly controlled based on the measured temperature of the liquefiedgas as a matter of course.

In step S130, the flow rate of the heat transfer media flowing into themedia heater 63 or the calories supplied to the heat transfer media bythe media heater 63 are changed according to the target temperature ofthe heat transfer media. In the present embodiment, in step S130, it ispossible to implement the cascade control of inducing the targettemperature of the heat transfer media based on the measured temperatureof the liquefied gas, and controlling a flow of the heat transfer mediabased on the target temperature of the heat transfer media, or it ispossible to implement direct control of changing a flow of the heattransfer media according to the measured temperature of the liquefiedgas, instead of using the target temperature of the heat transfer media.Detailed contents of the control of the flow of the heat transfer mediain step S130 will be described in detail with reference to FIG. 4.

FIG. 4 is a detailed flowchart of step S130 of the liquefied gastreatment method according to the first embodiment of the presentinvention.

As illustrated in FIG. 4, step S130 of the liquefied gas treatmentmethod according to the first embodiment of the present inventionincludes causing at least some of the heat transfer media to bypass themedia heater 63, in such a manner that the flow rate of the heattransfer media bypassing the media heater 63 is controlled (S131),controlling driving of the media pump 62 supplying the heat transfermedia to the media heater 63 (S132), and controlling the amount of heatsources supplied to the heat transfer media flowing into the mediaheater 63 (S133).

In step S131, at least some of the heat transfer media bypasses themedia heater 63, in such a manner that the flow rate of the heattransfer media bypassing the media heater 63 is controlled. To this end,in the present embodiment, the aforementioned branch line 65 may beused.

The heat transfer media flow into the media heater 63 through the mediapump 62, and some of the heat transfer media flows to the downstream ofthe media heater 63 via the branch line 65 by the bypass adjusting valve651 provided on the branch line 65, and the remaining heat transfermedia flow into the media heater 63 to be heated by steam and the likein the media heater 63.

In this case, as the flow rate of the heat transfer media bypassing themedia heater 63 is large, the temperature of the heat transfer media atthe downstream of the media heater 63, that is, the upstream of the heatexchanger 50, may be decreased, and to the contrary, as the flow rate ofthe heat transfer media bypassing the media heater 63 is small, thetemperature of the heat transfer media flowing into the heat exchanger50 may be increased.

In other words, in step S131, when the measured temperature of theliquefied gas is lower than the demanded temperature of the liquefiedgas of the source of demand 20, the controller 90 may decrease the flowrate of the heat transfer media bypassing the media heater 63 accordingto the calculated target temperature of the heat transfer media so as tomeet the demanded temperature of the liquefied gas of the source ofdemand 20, but on the contrary, when the measured temperature of theliquefied gas is higher than the demanded temperature of the liquefiedgas of the source of demand 20, the controller 90 may decrease thetemperature of the heat transfer media flowing into the heat exchanger50 by increasing the flow rate bypassing the media heater 63 based onthe target temperature of the heat transfer media calculated by thetarget temperature calculator 91.

In step S132, the driving of the media pump 62 supplying the heattransfer media to the media heater 63 is controlled. In step S131, someof the heat transfer media bypasses the media heater 63, but in stepS132, a flow of the heat transfer media flowing into the media heater 63may be changed.

In other words, in the present embodiment, it is possible to change theflow rate supplied to the media heater 63 from the media pump 62 bycontrolling a speed or a pressure of the media pump 62, and thus similarto step S131, the heat transfer media may be heated to the targettemperature by the media heater 63 to flow into the heat exchanger 50.

In step S133, the amount of heat sources supplied to the heat transfermedia flowing into the media heater 63 is controlled. In steps S131 andS132, the flow rate of the heat transfer media flowing into the mediaheater 63 may be controlled, but in step S133, the amount of heatsources supplied by the media heater 63 may be controlled. In this case,the heat source may be steam, and the amount of heat sources may beadjusted by adjusting a degree of opening of the heat source supply line66 connected to the media heater 63. The degree of opening of the heatsource supply line 66 may be implemented by the heat source supply valve661 provided on the heat source supply line 66.

When the amount of heat sources is changed, the calories of the heattransfer media heated by and discharged from the media heater 63 may bechanged, and thus, the heat transfer media are heated to the targettemperature, so that the heat transfer media may sufficiently heat theliquefied gas to the demanded temperature of the source of demand 20 inthe heat exchanger 50.

As described above, in the present embodiment, it is possible to easilycontrol the temperature of the liquefied gas to be appropriate to thedemanded temperature of the liquefied gas of the source of demand 20 byimplementing the cascade control of calculating the target temperatureof the heat transfer media based on the measured temperature of theliquefied gas, and adjusting the flow rate of the heat transfer mediasupplied to the media heater 63 through the target temperature of theheat transfer media or the amount of calories supplied to the heattransfer media by the media heater 63.

FIG. 5 is a flowchart of a liquefied gas treatment method according to asecond embodiment of the present invention.

As illustrated in FIG. 5, the liquefied gas treatment method accordingto the second embodiment of the present invention includes setting acoagulation prevention reference value for preventing heat transfermedia from being coagulated (S210), detecting a state of the heattransfer media circulating through the media heater 63 and the heatexchanger 50 (S220), and changing a flow rate of the heat transfer mediaflowing into the media heater 63 or calories supplied to the heattransfer media by the media heater 63 based on a state value of the heattransfer media and the coagulation prevention reference value (S230).

In step S210, the coagulation prevention reference value for preventingthe heat transfer media from being coagulated (a material included inthe heat transfer media may be coagulated) is set. The heat transfermedia may be glycol water and consist of water and ethylene glycol. Inthis case, when the heat transfer media are cooled to be in an extremelylow temperature state, water is frozen to disturb use of the heattransfer media. Accordingly, in step S210, a temperature for preventingwater included in the heat transfer media from being frozen, that is,the coagulation prevention reference value, may be set, and thecoagulation prevention reference value may be, for example, 30° C., butis not limited thereto.

In step S220, the state of the heat transfer media circulating throughthe media heater 63 and the heat exchanger 50 is detected. The state ofthe heat transfer media may be the temperature of the heat transfermedia, and the temperature of the heat transfer media may be detecteddownstream of or in the heat exchanger 50.

In other words, the state of the heat transfer media means thetemperature of the heat transfer media cooled by the liquefied gas inthe heat exchanger 50, and when it is determined that the heat transfermedia are supercooled, the temperature of the heat transfer media may beincreased in step S230.

In step S230, the flow rate of the heat transfer media flowing into themedia heater 63 or the calories supplied to the heat transfer media bythe media heater 63 are changed based on the state value of the heattransfer media and the coagulation prevention reference value. In stepS230, the state value of the heat transfer media may be equal to orgreater than the coagulation prevention reference value, and step S230will be described in detail with reference to FIG. 6 below.

FIG. 6 is a detailed flowchart of step S230 of the liquefied gastreatment method according to the second embodiment of the presentinvention.

As illustrated in FIG. 6, step S230 of the liquefied gas treatmentmethod according to the second embodiment of the present inventionincludes causing at least some of the heat transfer media bypass themedia heater 63, in such a manner that the flow rate of the heattransfer media bypassing the media heater 63 is controlled (S231),controlling driving of the media pump 62 supplying the heat transfermedia to the media heater 63 (S232), and controlling the amount of heatsources supplied to the heat transfer media flowing into the mediaheater 63 (S233).

In step S231, at least some of the heat transfer media bypasses themedia heater 63, in such a manner that the flow rate of the heattransfer media bypassing the media heater 63 is controlled. Thecontrolling of the flow rate of the heat transfer media bypassing themedia heater 63 is the same as that described in step S131. However, inthe present embodiment, step S231 is different from step 131 in thatwhen the heat transfer media are cooled in the heat exchanger 50, thetemperature of the cooled heat transfer media is compared with thecoagulation prevention reference value to change a degree of opening ofthe bypass adjusting valve 651.

In other words, when the temperature of the heat transfer mediadischarged from the heat exchanger 50 is lower than the coagulationprevention reference value, the controller 90 decreases the degree ofopening of the bypass adjusting valve 651 and thus causes most of theheat transfer media to flow into the media heater 63, so that the icingphenomenon is prevented from being generated even though the heattransfer media are cooled in the heat exchanger 50.

In step S232, the driving of the media pump 62 supplying the heattransfer media to the media heater 63 is controlled. The control of thedriving of the media pump 62 is the same as that described in step S132,so that in the present embodiment, the RPM of the media pump 62 and thelike may be adjusted in order to prevent the icing of the heat transfermedia. In other words, when the temperature of the heat transfer mediaat the downstream of the heat exchanger 50 is detected to be equal to orlower than the coagulation prevention reference value, it is possible toincrease total calories of the heat transfer media supplied to the heatexchanger 50 by increasing the RPM of the media pump 62. Accordingly,even though the heat transfer media lose heat to the liquefied gas, theicing phenomenon is prevented from being generated.

In step S233, the amount of heat sources supplied to the heat transfermedia flowing into the media heater 63 is controlled. The amount of heatsources supplied to the heat transfer media flowing into the mediaheater 63 may be controlled by the adjustment of the degree of openingof the heat resource supply valve 661 as described in step S133.

When it is detected that the temperature of the heat transfer media isequal to or lower than the coagulation prevention reference value, thedegree of opening of the hear resource supply valve 661 is increased,and thus the heat transfer media receive the relatively large amount ofheat resources (steam and the like) from the media heater 63 to flowinto the heat exchanger 50, so that even though the heat transfer mediaare cooled during the heat exchange with the liquefied gas, waterincluded in the heat transfer media is not frozen.

Further, in the present embodiment, the method may further includedischarging the heat transfer media flowing into the heat exchanger 50to the outside based on the state value of the heat transfer media andthe coagulation prevention reference value (S240).

Step S240 is performed for the purpose of preparing the case in whichthe heat transfer media are iced in the heat exchanger 50. For example,when a problem is generated in the media circulation, even though theheat transfer media flow into the heat exchanger 50 while havingsufficient calories, the heat transfer media may be supercooledaccording to the continuous cooling by the liquefied gas, andperformance of the heat exchanger 50 may be degraded, or even worse, thesystem may be stopped.

Accordingly, in step S240, when the temperature in or downstream of theheat exchanger 50, which is the state value of the heat transfer media,is lower than the coagulation prevention reference value, it isestimated that the risk of the icing phenomenon is increased, and theheat transfer media remaining in the heat exchanger 50 may be dischargedto the outside.

In this case, the discharged heat transfer media may return to the mediatank 61 or the media pump 62 along the media discharge line 93, and maybe stored in the temporary media storing tank 95 and then processed.

As described above, in the present embodiment, it is possible to preventwater included in the heat transfer media from being frozen due to thesupercooling of the heat transfer media, which are heated by the mediaheater 63 to flow into the heat exchanger 50, by the liquefied gas, andwhen a problem is generated in the media circulation so that the risk ofthe icing phenomenon in the heat transfer media remaining in the heatexchanger 50 is increased, the heat transfer media are discharged to theoutside through the media discharge line 93, thereby preventing theicing phenomenon of the heat transfer media and preventing the heatexchanger 50 from being damaged.

FIG. 7 is a flowchart of a liquefied gas treatment method according to athird embodiment of the present invention.

As illustrated in FIG. 7, the liquefied gas treatment method accordingto the third embodiment of the present invention includes setting agasification prevention reference value for preventing heat transfermedia from being gasified (S310), detecting a state of the heat transfermedia circulating through the media heater 63 and the heat exchanger 50(S320), and changing a flow rate of the heat transfer media flowing intothe media heater 63 or calories supplied to the heat transfer media bythe media heater 63 based on a state value of the heat transfer mediaand the gasification prevention reference value (S330).

In step S310, the gasification prevention reference value for preventingthe heat transfer media from being gasified (a material included in theheat transfer media may be gasified) is set. The heat transfer media maybe glycol water similar to the second embodiment, and when the heattransfer media are glycol water, water is included in the heat transfermedia, so that when the heat transfer media are overheated, water may beevaporated.

Accordingly, in the present embodiment, in order to prevent the heattransfer media from being overheated in the media heater 63, thegasification prevention reference value may be set, and the gasificationprevention reference value may be a temperature for preventing the waterincluded in the heat transfer media from being gasified, and forexample, 95° C., but the present invention is not limited thereto.

In step S320, the state of the heat transfer media circulating throughthe media heater 63 and the heat exchanger 50 is detected. The state ofthe heat transfer media may be the temperature of the heat transfermedia flowing from the downstream of the media heater 63 to the heatexchanger 50, and in this case, the temperature of the heat transfermedia may be a temperature before or after the heat transfer mediabypassing the media heater 63 are joined.

In step S330, the flow rate of the heat transfer media flowing into themedia heater 63 or the calories supplied to the heat transfer media bythe media heater 63 are changed based on the state value of the heattransfer media and the gasification prevention reference value. In stepS330, the state value of the heat transfer media may be lower than thegasification prevention reference value, and detailed contents thereofwill be described below with reference to FIG. 8.

FIG. 8 is a detailed flowchart of step S330 of the liquefied gastreatment method according to the third embodiment of the presentinvention.

As illustrated in FIG. 8, step S330 of the liquefied gas treatmentmethod according to the third embodiment of the present invention mayinclude causing at least some of the heat transfer media bypass themedia heater 63, in such a manner that the flow rate of the heattransfer media bypassing the media heater 63 is controlled (S331),controlling driving of the media pump 62 supplying the heat transfermedia to the media heater 63 (S332), and controlling the amount of heatsources supplied to the heat transfer media flowing into the mediaheater 63 (S333).

In step S331, at least some of the heat transfer media bypasses themedia heater 63, in such a manner that the flow rate of the heattransfer media bypassing the media heater 63 is controlled. The contentsof the adjustment of the flow rate of the heat transfer media bypassingthe media heater 63 in step S331 are similar to those of aforementionedsteps S131 and S231, but the present embodiment is provided for thepurpose of preventing the heat transfer media from being overheated atthe downstream of the media heater 63, so that when the temperature ofthe heat transfer media is higher than the gasification preventionreference value, a degree of opening of the bypass adjusting valve 651may be increased. When the degree of opening of the bypass adjustingvalve 651 is increased, the cracking risk may be decreased when the heattransfer media passing through the media heater 63 and the heat transfermedia bypassing the media heater 63 are joined.

In step S332, the driving of the media pump 62 supplying the heattransfer media to the media heater 63 is controlled. Step S332 is alsosimilar to steps S132 and S232, and when the temperature of the heattransfer media is detected to be higher than the gasification preventionreference value, on an assumption that uniform hear sources (steam andthe like) are supplied to the heat transfer media by the media heater63, it is possible to prevent the heat transfer media from beingoverheated by steam by increasing RPM of the media pump 62 and thusincreasing the flow rate of the heat transfer media supplied to themedia heater 63.

In step S333, the amount of heat sources supplied to the heat transfermedia flowing into the media heater 63 is controlled. Step S333 is alsosimilar to steps S133 and S233, and the present embodiment is providedfor the purpose of preventing the cracking phenomenon of the heattransfer media, so that it is possible to reduce the amount of heatsources supplied to the heat transfer media as necessary based on thetemperature of the heat transfer media and the gasification preventionreference value.

Further, in the present embodiment, the method further includesdischarging a material (which may be the heat transfer media or amaterial included in the heat transfer media) gasified from the heattransfer media discharged from the media heater 63 to the outside (notshown), and the remaining heat transfer media except for the gasifiedmaterial flow into the heat exchanger 50, thereby smoothly heating theliquefied gas.

As described above, in the present embodiment, when the heat transfermedia are heated by the media heater 63 to flow into the heat exchanger50, the heat transfer media are prevented from being overheated by themedia heater 63, thereby preventing the cracking phenomenon of the heattransfer media.

FIG. 9 is a flowchart of a liquefied gas treatment method according to afourth embodiment of the present invention.

As illustrated in FIG. 9, the liquefied gas treatment method accordingto the fourth embodiment of the present invention includes measuring atemperature of liquefied gas supplied to the source of demand 20 (S410),detecting a state of heat transfer media circulating through the mediaheater 63 and the heat exchanger 50 (S420), and decreasing a flow rateof the heat transfer media flowing into the media heater 63 while themeasured temperature of the liquefied gas becomes equal to or greaterthan a demanded temperature of the source of demand 20 (S430).

In step S410, the temperature of the liquefied gas supplied to thesource of demand 20 is measured. The temperature of the liquefied gas ismeasured by the liquefied gas temperature sensor 70, and when theliquefied gas temperature sensor 70 is provided between the heatexchanger 50 and the source of demand 20, the measured temperature ofthe liquefied gas may be a temperature after being heated by the heattransfer media in the heat exchanger 50.

In step S420, the state of the heat transfer media circulating throughthe media heater 63 and the heat exchanger 50 is detected. In step S420,a difference between temperatures of the heat transfer media at thefront and rear ends of the heat exchanger 50 may be detected. Thedifference between the temperatures means a difference between thetemperatures detected by the first media state detecting sensor 81 andthe second media state detecting sensor 82, respectively, and the firstmedia state detecting sensor 81 is provided at the upstream of the heatexchanger 50, and the second media state detecting sensor 82 is providedat the downstream of the heat exchanger 50 on the media circulation line64, so that the difference between the temperatures may be a valueobtained by subtracting the temperature of the second media statedetecting sensor 82 from the temperature of the first media statedetecting sensor 81.

The difference between the temperatures of the heat transfer media maymean the calories supplied to the liquefied gas by the heat exchanger50. In this case, in order to accurately measure the calories, in stepS420, the flow rate of the heat transfer media may be consideredtogether, and the flow rate of the heat transfer media may be measuredby the media flow rate sensor 671.

When the difference between the temperatures of the heat transfer mediaand the flow rate of the heat transfer media are obtained, the caloriessupplied to the liquefied gas by the heat exchanger 50 may becalculated. Accordingly, in the present embodiment, it may be understoodthat the difference between the temperatures of the heat transfer medianeeds to be equal to or greater than a predetermined value through acomparison between the temperature of the liquefied gas measured in stepS410 and the demanded temperature of the liquefied gas of the source ofdemand 20.

In step S430, the measured temperature of the liquefied gas may be equalto or greater than the demanded temperature of the source of demand 20,and the flow rate of the heat transfer media flowing into the mediaheater 63 is decreased (minimized). In order to cause the measuredtemperature of the liquefied gas to be equal to or greater than thedemanded temperature of the source of demand 20, the calories of theheat transfer media need to be sufficiently obtained. Accordingly, instep S430, the difference between the temperatures of the heat transfermedia at the front and rear ends of the heat exchanger 50 may be equalto or greater than a predetermined value while decreasing the flow rateof the heat transfer media flowing into the media heater 63.

In this case, the predetermined value may be calculated based on themeasured temperature of the liquefied gas, the demanded temperature ofthe source of demand 20, the flow rate of the heat transfer media, andthe like, and a calculation process may be performed based on a generalcalorie calculation.

Hereinafter, contents of the decrease in the flow rate of the heattransfer media flowing into the media heater 63 in step S430 will bedescribed in detail with reference to FIG. 10.

FIG. 10 is a detailed flowchart of step S430 of the liquefied gastreatment method according to the fourth embodiment of the presentinvention.

As illustrated in FIG. 10, step S430 of the liquefied gas treatmentmethod according to the fourth embodiment of the present invention mayinclude controlling driving of the media pump 62 supplying the heattransfer media to the media heater 63 (S431), and controlling a degreeof opening of the flow rate adjusting valve 67 provided at the upstreamof the media heater 63 (S432).

In step S431, the driving of the media pump 62 supplying the heattransfer media to the media heater 63 is controlled. Step S431 issimilar to steps S132, S232, and S332. According to the presentembodiment, it is possible to improve efficiency of media pump 62 anddecrease energy consumption by minimizing the driving of the media pump62. In other words, in the present embodiment, the difference betweenthe temperatures of the heat transfer media at the front and rear endsof the heat exchanger 50 is sufficiently ensured, and the flow rate ofthe heat transfer media may be decreased by reducing the driving of themedia pump 62. In this case, whether the difference between thetemperatures of the heat transfer media is sufficiently ensured may beidentified by each media state detecting sensor 80.

In step S432, the degree of opening of the flow rate adjusting valve 67provided at the upstream of the media heater 63 is controlled. The flowrate adjusting valve 67 may be provided at the upstream of the mediaheater 63 as aforementioned in the liquefied gas treatment system 2. Theflow rate adjusting valve 67 may change the flow rate of the heattransfer media flowing into the media heater 63 by the adjustment of thedegree of opening, and may be provided at the downstream of the mediapump 62.

The degree of opening of the flow rate adjusting valve 67 may bedecreased (minimized) within a range in which the liquefied gas issufficiently heated to the demanded temperature of the liquefied gas ofthe source of demand 20. Even though the degree of opening of the flowrate adjusting valve 67 is decreased, the difference between thetemperatures of the heat transfer media at the front and rear ends ofthe heat exchanger 50 is maintained to be equal to or greater than apredetermined value, so that the liquefied gas may sufficiently receivecalories.

In the present embodiment, step S431 and step S432 are separatelyperformed. However, step S431 and step S432 may be simultaneouslydriven, so that RPM of the media pump 62 may be adjusted and the degreeof opening of the flow rate adjusting valve 67 may be adjusted.

As described above, according to the present embodiment, the liquefiedgas is heated so as to meet the demanded temperature of the liquefiedgas of the source of demand 20 in the heat exchanger 50, and the flowrate of the heat transfer media passing through the heat exchanger 50,the media pump 62, and the like along the media circulation line 64 isdecreased, thereby improving efficiency of the media pump 62.

DESCRIPTION OF MAIN REFERENCE NUMERALS OF DRAWINGS

 1: Liquefied gas processign system in the related art  2: Liquefied gasprocessign system of the presnet invention  10: Liquefied gas storingtank  20: Source of demand  21: Liquefied gas supply line  30: Pump  31:Boosting pump  32: High-pressure pump  40: Electric heater  50: Heatexchanger  60: Media supply device  61: Media tank  62: Media pump  63:Media heater  64: Media circulation line  65: Branch line 651: Bypassadjusting valve  66: Heat resource supply line  67: Flow rate adjustingvalve 671: Media flow rate sensor 661: Heat source supply valve  70:Liquefied gas temperature sensor  80: Media state detecting sensor  81:First media state detecting sensor  82: Second media state detectingsensor  90: Controller  91: Target temperature calculator  92: Phaseseparator  93: Media discharge line  94: Media discharge valve  95:Temporary media storing tank

1. A liquefied gas treatment system, comprising: a liquefied gas supplyline connected from a liquefied gas storing tank to a source of demand;a heat exchanger provided on the liquefied gas supply line between thesource of demand and the liquefied gas storing tank and configured toexchange heat between the liquefied gas supplied from the liquefied gasstoring tank and heat transfer media; a media heater configured to heatthe heat transfer media; a media circulation line connected from themedia heater to the heat exchanger; a liquefied gas temperature sensorprovided on the liquefied gas supply line and configured to measure atemperature of the liquefied gas, and a controller configured to causethe measured temperature of the liquefied gas to be equal to or higherthan a demanded temperature of the source of demand in such a mannerthat the controller decreases a flow rate of the heat transfer mediaflowing into the media heater.
 2. The liquefied gas treatment system ofclaim 1, further comprising: a media tank configured to store the heattransfer media; and a media pump configured to supply the heat transfermedia stored in the media tank to the media heater, wherein thecontroller controls the flow rate of the heat transfer media supplied tothe media heater from the media pump by controlling driving of the mediapump.
 3. The liquefied gas treatment system of claim 2, wherein thecontroller controls the flow rate of the heat transfer media byadjusting RPM of the media pump.
 4. The liquefied gas treatment systemof claim 1, further comprising; a flow rate adjusting valve provided onthe media circulation line and configured to adjust the flow rate of theheat transfer media flowing into the media heater, wherein thecontroller controls the flow rate of the heat transfer media byadjusting a degree of opening of the flow rate adjusting valve.
 5. Theliquefied gas treatment system of claim 1, further comprising: a mediaflow rate sensor provided on the media circulation line and configuredto measure the flow rate of the media transfer media flowing into themedia heater.
 6. The liquefied gas treatment system of claim 1, whereinthe liquefied gas temperature sensor is provided between the heatexchanger and the source of demand on the liquefied gas supply line. 7.The liquefied gas treatment system of claim 1, further comprising: amedia state detecting sensor provided on the media circulation line andconfigured to measure a state of the heat transfer media.
 8. Theliquefied gas treatment system of claim 7, wherein the media statedetecting sensor detects a difference between temperatures of the heattransfer media at front and rear ends of the heat exchanger, and thecontroller causes the difference between the temperatures of the heattransfer media to be equal to or greater than a predetermined value insuch a manner that the controller decreases the flow rate of the heattransfer media flowing into the media heater.
 9. The liquefied gastreatment system of claim 7, wherein the media state detecting sensorincludes: a first media state detecting sensor configured to detect atemperature of the heat transfer media at a downstream of the mediaheater; and a second media state detecting sensor configured to detect atemperature of the heat transfer media downstream of or in the heatexchanger, and the controller causes a difference between a measuredtemperature by the first media state detecting sensor and a measuredtemperature by the second media state detecting sensor to be equal to orgreater than a predetermined value in such a manner that the controllerdecreases the flow rate of the heat transfer media flowing into themedia heater.
 10. The liquefied gas treatment system of claim 1, furthercomprising: a pump provided on the liquefied gas supply line andconfigured to pressurize the liquefied gas discharged from the liquefiedgas storing tank, wherein the heat exchanger exchanges heat between theliquefied gas supplied from the pump and the heat transfer media. 11.The liquefied gas treatment system of claim 1, wherein the heat transfermedia are glycol water.
 12. A liquefied gas treatment method inassociation with a method of driving a liquefied gas treatment systemwhich heats liquefied gas with heat transfer media in a heat exchanger,in such a manner that a media heater heats and supplies the heattransfer media to the heat exchanger, the liquefied gas treatment methodcomprising: measuring a temperature of the liquefied gas supplied to thesource of demand; and causing the measured temperature of the liquefiedgas to be equal to or higher than a demanded temperature of the sourceof demand in such a manner that a flow rate of the heat transfer mediaflowing into the media heater is decreased.
 13. The liquefied gastreatment method of claim 12, wherein the measuring of the temperatureof the liquefied gas includes measuring the temperature of the liquefiedgas between the heat exchanger and the source of demand.
 14. Theliquefied gas treatment method of claim 12, further comprising:detecting a state of the heat transfer media.
 15. The liquefied gastreatment method of claim 14, wherein the detecting of the state of theheat transfer media includes detecting a difference between temperaturesof the heat transfer media at front and rear ends of the heat exchanger,and the decreasing of the flow rate of the heat transfer media orcalories supplied to the heat transfer media includes causing thedifference between the temperatures of the heat transfer media at thefront and rear ends of the heat exchanger to be equal to or greater thana predetermined value in such a manner that the flow rate of the heattransfer media flowing into the media heater is decreased.
 16. Theliquefied gas treatment method of claim 12, wherein the decreasing ofthe flow rate of the heat transfer media includes controlling driving ofthe media pump supplying the heat transfer media to the media heater.17. The liquefied gas treatment method of claim 16, wherein thecontrolling of the driving of the media pump includes adjusting RPM ofthe media pump.
 18. The liquefied gas treatment method of claim 12,wherein the decreasing of the flow rate of the heat transfer mediaincludes controlling a degree of opening of a flow rate adjusting valveprovided upstream of the media heater.